Nitrile polymeric blends

ABSTRACT

A polymeric blend is prepared from a nitrile polymer and a modifying polymer containing dicyanobutene-1. The modifying polymer greatly improves the processability of the nitrile polymer while maintaining or improving the barrier properties thereof, and products molded from the blends exhibit better optical characteristics than products similarly produced from the unmodified nitrile polymer.

United States Patent Yoon Chai Lee;

Quirino A. Trementozzi, both of Springfield, Mass.

Jan. 3, 1969 Sept. 2 l 197 l Monsanto Company St. Louis, Mo.

Inventors Appl. No. Filed Patented Assignee NlTRlLE POLYMERIC BLENDS 9Claims, No Drawings US. Cl 260/876 R, 260/4 R, 260/785 N, 260/878 R,260/879, 260/880 R, 260/885, 260/887, 260/893, 260/898 Int. Cl C08f37/18, C08f41/l2 Field of Search 260/876, 898, 887, 893, 880

Primary Examiner-Murray Tillman Assistant Examiner-H. RobertsAttorneys-H. B. Roberts, A. E. Hoffman and P. J. Hogan ABSTRACT: Apolymeric blend is prepared from a nitrile"- polymer and a modifyingpolymer containing dicyanobutencl. The modifying polymer greatlyimproves the processability of the nitrile polymer while maintaining orimproving the barrier properties thereof, and products molded from theblends exhibit better optical characteristics than products similarlyproduced from the unmodified nitrile polymer.

BACKGROUND OF THE INVENTION Polymers prepared from a major amount of anitrile monomer such as acrylonitrile, methacrylonitrile, etc., havebeen found to possess many desirable properties including particularlyoutstanding oxygen and water-vapor barrier characteristics. Theirwidespread use has been limited, however, largely because of thedifficulties in molding, extruding and otherwise processing the resin,and because of the undesirable coloration which tends to occur in theproducts produced therefrom.

Numerous processing aids are available and have been employed in thenitrile polymers, but, so far as is known, none of the resins soproduced have been entirely satisfactory for extensive commercial.application. Although the processing characteristics of the polymer canbe improved by various processing aids, normally the levels ofimprovement achieved are not adequate and/or the presence of theprocessing aid seriously detracts from other desirable properties of thematrix resin including chemical and heat resistance and particularly thebarrier properties thereof.

Accordingly, it is an object of the present invention to provide novelphysical blends of nitrile polymers wherein a desirable balance ofphysical properties and processing characteristics is obtained.

It is also an object to provide nitrile polymeric blends adapted to usein packaging and other applications and which exhibit low gaspermeability along with good processing characteristics.

Still another object is to provide novel blends of nitrile polymers fromwhich superior molded and extruded products can be produced convenientlyand relatively economically.

SUMMARY OF THE INVENTION It has now been found that the foregoing andrelated objects may be readily attained in a blend comprising about 55.0to 97.0 weight percent of a nitrile polymer and about 45.0 to 3.0percent by weight of a modifying polymer compatible therewith. Thenitrile polymer contains at least 15.0 percent by weight of anethylenically unsaturated nitrile selected from the group consisting ofacrylonitrile, methacrylonitrile, and mixtures thereof; the modifyingpolymer contains at least 5.0 percent by weight of dicyanobutene-l andmay contain up to 95.0 percent by weight of at least one copolymerizablemonomer selected from the class consisting of ethylenically unsaturatednitriles, monovinylidene aromatic hydrocarbons, alkyl (alk)acrylates,dialkyl maleates and dialkyl fumarates. At least about 60.0 percent byweight of the blend is comprised of monomers containing the cyanidegroup. There may be included in the blend a rubbery polymer which iseither grafted by the dycanobutene-l polymer or by the nitrile polymeror which is physically admixed therewith, the total concentration ofsuch a rubber being limited to not more than about 20.0 percent byweight of the blend.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As indicated, theblends of the present invention comprise a nitrile polymer and amodifying polymer of dicyanobutene-l. The blend contains about 3.0-45.0weight percent of the dicyanobutene-l polymer and about 97.0-55.0percent of the nitrile polymeric matrix. Preferably, the modifyingpolymer is an interpolymer with at least 20.0 weight percent of at leastone copolymerizable monomer, and comprises about 5.0 to 30.0 percent ofthe blend; most desirably it is about 10.0 to 20.0 percent of the blendfor optimum properties and processability. In addition as has beenmentioned, it is important that at least 60.0 weight percent of theblend be provided by a cyanide-containing compound, including theethylenically unsaturated nitriles, dicyanobutenes, etc. The source ofthe cya nide compound is not critical, and it may be in the matrix ormodifying polymers, or in included rubbers, whether grafted or not.

The Nitrile Polymer The polymer which serves as the matrix is anunsaturated nitrile polymer, i.e., a polymer containing at least 15 .0percent by weight of an ethylenically unsaturated nitrile of the groupconsisting of acrylonitrile, methacrylonitrile and mixtures thereof.Suitable matrix polymers include homopolymers of these unsaturatednitriles as well as interpolymers of at least 15.0 percent by weight ofone or more of them with up to 85.0 percent by weight of one or morecopolymerizable monomers. Exemplary of such monomers are otherethylenically unsaturated nitriles such as ethacrylonitrile andpropacrylonitrile, monovinylidene aromatic hydrocarbons (e.g., styrene;ar-alkylstyrenes such as the 0-, m-, and p-methylstyrenes, 2,4-dimethylstyrene ar-ethylstyrenes, p-t-butylstyrene, etc.;alphaalkylstyrenes such as alpha-fmethylstyrene, alpha-ethylstyrene,alpha-methyl p-methylstyrene, etc.; vinyl naphthalene, and mixturesthereof), alkyl (alk)acrylates (e.g., methyl ac late, ethyl acrylate,propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, thecorresponding alkyl methacrylates, etc.; and mixtures thereof),acrylamides (e.g., acrylamide; methacrylamide; N-alkyl acrylamides suchas N-methyl acrylamide, N- butyl acrylamide, etc.; and mixturesthereof), dialkyl maleates and fumarates (e.g., diethyl maleate, dibutylfumarate, etc, and mixtures thereof), etc. Many other unsaturatednitrile polymers which contain at least 15.0 percent by weight ofcombined unsaturated nitrile and which present a processing andcoloration problem because of their unsaturated nitrile content will beobvious to those skilled in the art. Normally the matrix polymer willcontain at least 50.0 percent, and preferably at least 75.0 percent, byweight of acrylonitrile and/or methacrylonitrile to achieve the desiredlevel of gas permeation resistance.

Exemplary of the nitrile polymers which may be used advantageously inaccordance with the present invention are acrylonitrile homopolymer;methacrylonitrile homopolymer; copolymers ofacrylonitrile/methacrylonitrile, acrylonitrile/styrene,methacrylonitrile/styrene, acrylonitrile/methacrylonitrile/styrene,acrylonitrile/alphamethylstyrene, methacrylonitrile/alpha-methylstyrene,acrylonitrile/ethacrylonitrilealpha-methylstyrene,ethacrylonitrile/alpha-methylstyrene, acrylonitrile/isobutylene,methacrylonitrile/isobutylene, acrylonitrile/vinyl acetate,acrylonitrile/methyl methacrylate,methacrylonitrile/ethacrylonitrile/alpha-methylstyrene, etc.;interpolymers containing four or more of the hereinbefore enumeratedmonomers may also be employed. (e.g., ar-alkylstyrene,such as the o-,mand p-methyl-styrenes 2,4-dimethylstyrene, the ar-ethylstyrenes,p-tert-butylstyrene, alphamethyl-p- A portion of the unsaturated nitrilepolymer may be grafted onto a rubbery substrate if so desired bypolymerizing the nitrile monomer or mixture thereof with copolymerizablemonomers in the presence of a preformed rubbery polymer. Numerousrubbery polymers may be used for this purpose and are enumeratedhereinafter; however, for best results it is highly desirable that thesubstrate rubber contain at least some unsaturation to facilitategrafting. Thus, the term nitrile polymer as used herein includes graftcopolymer blends as well as the ungrafted ethylenically unsaturatednitrile homopolymers and copolymers. Normally, the matrix resinsemployed herein will have weight average molecular weights of at leastabout 150,000. Although the presence of the modifying polymer isbeneficial in all matrices described herein, it is particularlybeneficial with the acrylonitrile polymers and the matrices havingweight average molecular weights of 250,000 and above.

The Modifying Polymer compounds dicyano-substituted in the 1,3-, 1,4-,or 2,4-positions. Normally the percentage of dicyanobutene-l in themodifying polymer will not exceed 80.0 percent by weight due toeconomics and the difficulty of preparing polymers containing suchmonomers in a high weight percentage. Preferably the amount of thedicyanobutene-l in the interpolymer is 10.0 to 50.0, and most desirablyabout 25.0 to 40.0, percent by weight thereof. The copolymerizablemonomer(s) of the dicyanobutene polymer may comprise about 95.0 to 20.0,preferably about 90.0 to 50.0 and most desirably about 75.0 to 60.0,percent by weight thereof. Exemplary of the monomers copolymerizablewith the dicyanobutenes are the ethylenically unsaturated nitriles(e.g., acrylonitrile, methacrylonitrile, ethacrylonitrile,propacrylonitrile, butacrylonitrile); the monovinylidene aromatichydrocarbons (e.g., styrene; ar-alkylstyrenes such as the m-, andp-methylstyrenes, 2,4- dimethylstyrene, ar-ethylstyrenes,p-t-butylstyrene, etc.; alpha-alkylstyrenes such asalpha-methylst'yrene, alpha-ethylstyrene, alpha-methyl-p-methylstyrene,etc. vinyl naphthalene; ring chlorinated derivatives of the foregoingmonovinylidene aromatic hydrocarbons); alkyl (alk)acrylates (e.g.,methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate,Z-ethylhexyl acrylate, the corresponding alkyl methacrylates, etc.);dialkyl maleates and fumarates (e.g., diethyl maleate, dibutyl fumarate,etc., and mixtures thereof), and mixtures of one or more of the monomersexemplified by the foregoing list may be used. Particularly preferredare the copolymerizable monomers of the group consisting of styrene,alpha-methyl styrene, acrylonitrile, methacrylonitrile, methylmethacrylate, and mixtures thereof. Although the dicyanobutenes mayproperly be considered nitriles, distinction is drawn herein betweenthem and the mononitriles such as acrylonitrile, methacrylonitrile,etc., herein termed ethylenically unsaturated nitriles.

A proportion of the preformed rubbery polymer, grafted with themodifying polymer, may also be incorporated therein by effecting thepolymerization of the monomers in the presence of the rubber. From apractical standpoint, the dicyanobutene polymers of the invention shouldcontain no more than about 20.0 percent by weight of the grafted rubber,and, when a rubber is included in the interpolymer, preferably it willbe present in an amount of about 5.0l5.0 percent. As in the case of agraft of the matrix monomers, numerous rubbers may be used in themodifying polymer but they most desirably contain some unsaturation tofacilitate grafting. Exemplary of the rubbers which are suitablesubstitutes in both the matrix and the modifying polymer are dienerubbers, natural rubbers, ethylene-propylene terpolymer rubbers, otherrubbery olefin polymers such as 'ethylene'vinyl acetate andethylene-octyl acrylate, and acrylate rubbers, such as butyl acrylateand 2-ethylhexyl acrylate, synthetic polyisoprene rubbers, and mixturesthereof. It will be appreciated that such rubbers include not onlyhomopolymers of the specifically identified constituents but alsointerpolymers which may be characterized primarily as the aforementionedrubbers.

The preferred substrates, however, are diene rubbers (including mixturesof diene rubbers), i.e., any rubbery polymer (a polymer having a secondorder transition temperature not higher than 0 C., preferably not higherthan -20 C., as determined by ASTM Test D746-52T) of one or more of theconjugated 1,3-dienes, e.g., butadiene, isoprene, piperylene,chloroprene, etc. Such rubbers include homopolymers and interpolymers ofconjugated l,3-dienes with up to an equal amount by weight of one ormore copolymerizable monoethylenically unsaturated monomers such asmonovinylidene aromatic hydrocarbons e.g., styrene; an ar-alkylstyrene,such as the 0-, mand p-methyl-styrenes 2,4-dimethylstyrene thear-ethylstyrenes, p-tert-butylstyrene, etc., an alphamethylstyrene,alpha-ethylstyrene, alpha-methyl-p-methylstyrene, etc.; vinylnaphthalene, etc. ar-halo monovinylidene aromatic hydrocarbons (e.g.,the 0-, mand p-chlorostyrenes, 2,4-di-bromostyrene,2-methyl-4-chlorostyrene, etc); acrylonitrile; methacrylonitrile; alkylacrylates (e.g., methyl acrylate, butyl acrylate, Z-ethylhexyl acrylate,etc.), the corresponding alkyl methacrylates; acrylamides (e.g.,acrylamide, methacrylamide, N-butylacrylamide, etc.); unsaturatedketones (e.g., vinyl methyl ketone, methyl isopropenyl ketone, etc.);alpha-olefins (e.g., ethylene, propylene, etc.; pyridines; and the like.

A preferred group of rubbers are those consisting essentially of750-1000 percent by weight of butadiene and/or isoprene and up to 25.0percent by weight of a monomer selected from the group consisting ofmonovinylidene aromatic hydrocarbons (e.g., styrene), and unsaturatednitriles (e.g., acrylonitrile), or mixtures thereof. Particularlyadvantageous substrates are butadiene homopolymers or interpolymers of80.0-95.0 percent by weight butadiene and 5.0-20.0 percent by weight ofacrylonitrile or styrene.

OPTlONAL COMPONENTS The blends of the present invention may be comprisedsolely of the nitrile polymeric matrix and the modifying dicyanobutenepolymer. However, significant advantages may often be realized whenadditional components are included in the blends. If neither themodifying polymer nor the matrix polymer is a graft copolymer blend, itmay be desirable to admix an impact modifier with the other twocomponents to improve the physical properties of the products producedfrom the blends, such as toughness, even through desirable physicalimprovements may be obtained simply by blending the dicyanobutene-lpolymer with the nitrile resin. In such a case the impact modifier maybe one of the previously mentioned rubbers evidencing sufficientcompatibility, or preferably a graft copolymer such as the ABS(acrylonitrile and styrene grafted upon a rubbery diene substrate) andM88 (methyl methacrylate and styrene grafted upon a rubbery dienesubstrate). Regardless of the source or mode of introduction of therubbery polymer, the total amount thereof should not exceed about 20.0percent of the total weight of the blend; preferably the amount thereofwill not be in excess of about 15.0 weight percent.

Other optional additives may also be included in the blends of theinvention, such as fillers, plasticizers, stabilizers, antioxidants andlubricants. The desirability of such additives will depend upon thecharacteristics of the blend and upon the optimum balance betweeneconomy and properties which can be attained thereby.

The copolymers and interpolymers employed in accordance with thisinvention may be prepared by any suitable method conventionally employedfor the production of polymers of that type. Thus, the polymers may beprepared en masse, in solution, suspension, emulsion or by a combinedmass/suspension technique; however, the aqueous dispersion techniquesare preferred.

Conventional agents for forming an emulsion of the monomers in waterwill be employed in the case of an emulsion polymerization process,exemplary of which are the fatty acid soaps, alkali metal or ammoniumsoaps of high molecular weight, alkyl or alkaryl sulfonates andsulfates, etc. On the other hand, if a suspension technique is employedsuitable suspension aids include the alkali metal salts of organicsulfonic acids, alkyl phenol/polyhydric alcohol condensation products,oil-soluble quaternary ammonium salts, water-soluble cellulosederivatives, etc.

Although thermally initiated reactions may be feasible, preferably asmall amount of a catalytic initiator is employed. Actinic radiation andboth water-soluble and monomer-soluble peroxy-type catalysts, with orwithout a reducing agent to form a redox system, may be used for thepolymerization reaction with variable efficacy depending upon theparticular polymerization technique employed. In some emulsionpolymerization processes, it is advantageous to use a redox system sinceit permits the use of slower catalysts with equivalent conversionperiods.

Exemplary of the water-soluble peroxy catalysts are the alkali metalperoxides; the alkali metal and ammonium persulfates, perborates,peracetates and percarbonates', and

The catalyst is generally included within the range of 0.001

to 2.0 percent by weight, and preferably on the order of 0.005 to 1.0percent by weight of the polymerizable material, depending upon themonomers, the polymerization technique, and the desired polymerizationcycle. An excess of catalyst during the initial period of polymerizationwill tend to favor the grafting reaction if a rubbery substrate isincluded.

Exemplary of the reducing agents which may be employed are alkali metaland ammonium sulfites, hydrosulfites, metabisulfites, thiosulfates,sulfinates, formaldehydesulfoxylates or ascorbic acid, dioxyacetone,dextrose, etc. Various other reducing agents for redox systems mayalso'be employed.

The amount of reducing agent will be about 0.001 to 1.0 percent byweight, and preferably on the order of 0.005 to 0.5 percent by weight,of the polymerizable monomer formulation, depending on the catalyst andthe amount thereof. For redox systems, minute amounts of activators orpromoters such as ferrous salts, cobalt and copper salts may beincluded.

Although it is possible to achieve substantially complete conversion ofmonomer to polymer (i.e., 100 percent) in certain of the formulationsdescribed herein, normally it is most economical and convenient toterminate the reaction short of completion, at about 85.0 to 90.0percent conversion;

generally the percentage of monomer converted will not be less thanabout 65.0. The cycle times for the reaction may vary widely and willdepend upon the particular techniques, reactants and initiator employed,but usually the reaction will be considered complete at the end of abouta 5- to 24- hour period. The suitable temperature for reaction will alsovary considerably, but will usually fall within the range of about to150 C.

BLENDING TECHNIQUES dried or coagulated. it will be appreciated that theblends may 5 5 be formed in the equipment for forming the product to bemade therefrom such as an extruder when the resin components are of thedesired particulate form. The conditions of molding or extrusion aregenerally the same as those which are used for comparable polymers, theprocessing temperature of the stock normally being in the range of about350 to 450 F. However, these factors will depend somewhat upon thecomponents and resultant blend properties.

Exemplary of the efficacy of the present invention are the followingspecific examples wherein all parts and percentages are on a weightbasis unless otherwise specified.

Example One and 10.0 percent 2,4-dicyanobutene-1. The interpolymer isprepared by an emulsion polymerization technique utilizing about 3.0percent, based upon the weight of polymerizable monomers in theformulation, of an emulsifying agent. The catalyst employed is potassiumpersulfate and the reaction is effected it about 75 C. for about 9 hoursuntil approximately percent of the monomers are polymerized.

Portions of this blend are subjected to testing in a capillary rheometerto determine the force necessary to achieve specified shear rates.Similar tests are performed utilizing specimens of the samemethacrylonitrile/styrene (90/10) copolymer from which any modifyingpolymer is omitted. in the apparatus used for testing the capillarydiameter is 0.0495 inch, the length:diameter ratio is 10:1 and theentrance angle is 90; the temperature of the material during the testsis maintained at about 380 F.

Each of the specimens is tested at three shear rates, i.e., 10, and1,000 second and the force necessary to maintain these rates ismeasured. Utilizing this information, the shear stresses and theapparent viscosities of each of the specimens is determined at each ofthe shear rates, and that data is set forth is table one. Since theseproperties of the materials are directly related to the processabilitythereof (i.e., the lower the shear stress and the apparent viscosity of'thematerial tested, the better will be is processability), these dataindicate the very significant improvements in processability which areattained by the present invention.

Viscosity (1b. see/in!) Shear rate Unmodifier? Apparent unmodified(second' Blend polymer blend polymer In all instances, the level ofdegradation producing coloration in the blends is found to besignificantly lower than in the unmodified copolymer, and the clarity ofthe specimens from the blends is excellent. in addition, gas permeationtests performed utilizing films formed in a heated hydraulic press fromeach of the foregoing materials show that in no case is the resistanceto the passage of gas, i.e., oxygen and water vapor, impairedsignificantly by the presence of the modifying copolymer. Thus, theblends of the present invention provide a film suitable for use as apackaging material where oxygen and water vapor barrier characteristicsare required.

Example Two Two series of tests are performed generally in accordancewith example one; in one series, a copolymer containing about 25.0percent of styrene and about 75.0 percent of 2,4- dicyanobutene-l issubstituted and in the other series a copolymer containing about 75.0percent of methacrylonitrile and 25.0 percent of a mixture of1,4-dicyanobutene-l and 2,4- dicyanobutene-l is used. In the firstseries, the matrix and modifying polymers are blended in same proportionas is used in example one; in the second series, about 30.0 percent ofthe modifying polymer is blended with about 70.0 percent of the nitrilepolymer.

in all instances, the present of the modifying copolymers producessignificant improvements in processability. The molded products exhibitgood levels of clarity and freedom from coloration, and there is noappreciable reduction in the resistance to gas permeation through filmsproduced from the blends.

Example Three A blend is prepared in the manner of example one by mixingabout 15 parts of a copolymer containing about 40.0 percent of2,4-dicyanobutene-1 and about 60.0 percent of alphamethylstyrene withabout 85 parts of an acrylonitrile homopolymer having a weight averagemolecular weight of about 300,000. Comparative tests demonstrate thatthe blend has a much higher level of processability than the unmodifiedhomopolymer; the color and clarity of articles produced from the blendare very good, and the resistance to gas permeation is excellent.

Thus, it can be seen that the present invention provides novel physicalblends of nitrile polymers wherein the physical properties andprocessing characteristics are well balanced. The desirable processingcharacteristics are coupled with improved or maintained resistance togas permeability to provide materials suitable for packaging and otherapplications. The blends provided may be readily molded and extruded toform superior products with improved optical characteristics. It shouldbe appreciated that although the nitrile polymer may contain as littleis 15.0 percent of ethylenically unsaturated nitrile, and although themodifying polymer may contain as little as 5.0 percent ofdicyano-butened and no other cyanidecontaining monomer, these lowerlimits can not be applied simultaneously since at least 60.0 percent byweight of the blend must be comprised of monomers containing the cyanidegroup.

What is claimed is l. A nitrile polymer blend comprising about 55.0 to97.0 weight percent of a nitrile polymer and about 45.0 to 3.0 weightpercent of a modifying interpolymer compatible therewith, said nitrilepolymer having a weight average molecular weight of at least about150,000 and containing at least 15.0 percent by weight of anethylenically unsaturated nitrile selected from the group consisting ofacrylonitrile, methacrylonitrile, and mixtures thereof, and up to 85.0percent by weight of at least one copolymerizable monomer elected fromthe group consisting of ethacrylonitrile, propacrylonitrile,monovinylidene aromatic hydrocarbons, alkyl (alk) acrylates,acrylamides, N-alkyl acrylamides, vinyl naphthalene, dialkyl maleatesand dialkylfumarates; said modifying interpolymer containing at least5.0 percent by weight of a dicyanobutene-l selected from the groupconsisting of l,3-dicyanobutene-l, l,4-dicyanobutene-l, and 2,4-dicyanobutene-4 l and 20.0 to 95.0 percent by weight of at least onecopolymerizable monomer selected from the class consisting ofethylenically unsaturated nitriles monovinylidene aromatic hydrocarbons,alkyl (alk)arcylates, dialkyl maleates and dialkyl fumarates, at leastabout 60.0 percent by weight of said blend being additionally ofmonomers containing the cyanide group. percent,

2. The blend of claim 1 additisnally containing up to about 20.0 percent, based upon the total weight of said blend, of a preformed rubberypolymer.

3. The blend of claim 1 comprising about 70.0 to 95.0 percent of saidnitrile polymer and about 30.0 to 5.0 weight percent of said modifyinginterpolymer, said nitrile polymer containing at least 50.0 percent byweight of said ethylenically unsaturated nitrile and said modifyinginterpolymer comprising about 10.0 to 50.0 weight percent ofdicyanobutene-l and about 90.0 to 50.0 weight percent of saidcopolymerizable monomer.

4. The blend of claim 1 comprising about 80.0 to 90.0 weight percent ofsaid nitrile polymer and about 20.0 to 10.0 weight percent of saidmodifying interpolymer, said nitrile polymer containing at least about75.0 weight percent of said ethylenically unsaturated monomer and saidmodifying interpolymer comprising about 25.0 to 40.0 weight percent ofdicyanobutene-l and about 75.0 to 60.0 weight percent of saidcopolymerizable monomer.

5. The blend of claim 2 wherein said preformed rubbery polymer is adiene rubber and at least a portion of said nitrile polymer is graftedthereupon.

6. The blend of claim 2 wherein said preformed rubbery polymer is adiene rubber present in an amount of about 5.0 to 15.0 percent basedupon the weight of said modifying interpolymer, and wherein at least aportion of said modifying interpolymer is grafted thereu on.

. he blend of claim wherein said nitrile polymer is selected from thegroup consisting of acrylonitrile homopolymers and copolymers thereofwith a monomer selected from the class consisting of styrene,alpha-alkyl styrenes, ring chlorinated analogs of styrene andalpha-alkyl styrenes, (alk)acrylic acids, (alk)acrylic acid esters,vinyl esters and mixtures thereof, said dicyanobutene-l being 2,4-dicyanobutene-l.

8. The blend of claim 1 wherein said nitrile polymer is selected fromthe group consisting of methacrylonitrile homopolymers and copolymersthereof with a monomer selected from the class consisting of styrene,alpha-alkyl styrenes, ring chlorinated analogs of styrene andalpha-alkyl styrenes, (alk)acrylic acids, (alk)acrylic acid esters andmixtures thereof, said dicyanobutene-l being 2,4dicyanobutenel.

9. The blend of claim 1 wherein said nitrile polymer has a weightaverage molecular weight of at least about 250,000.

@253? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,507,978 Dated SepTember 2|, I97! Inventofls) Yoon C. Lee & Quirino A.TremenTozzi It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 4|, delere "e rhacryloniTri lealpha-meThylsTyrene".

Column 2, delere lines 47-50 beginning "(e.g., ara|ky|-".

Column 4, line 3, afTer "efc." inserf a arenrhesis Column 4, ine 25,dele re "Through and inser' r Though Column 7, Claim l, line 10, delere"elecfed" and insem selecrec! Column 7, Claim I, line 17, delefe"dicyanoburenel I" and inserf dicyanobu+enel Column 8, Claim 2, linedeIeTe "addirisnally" and inserr addiTional 1y Signed and seale d this29th day of February 1972 (SEAL) Attest:

EDWARD I LFLETCHER JR. ROBERT GOTTSCHALK Abtestinp; Office ICommissionerof Patents

2. The blend of claim 1 additisnally containing up to about 20.0 percent, based upon the total weight of said blend, of a preformed rubberypolymer.
 3. The blend of claim 1 comprising about 70.0 to 95.0 percentof said nitrile polymer and about 30.0 to 5.0 weight percent of saidmodifying interpolymer, said nitrile polymer containing at least 50.0percent by weight of said ethylenically unsaturated nitrile and saidmodifying interpolymer comprising about 10.0 to 50.0 weight percent ofdicyanobutene-1 and about 90.0 to 50.0 weight percent of saidcopolymerizable monomer.
 4. The blend of claim 1 comprising about 80.0to 90.0 weight percent of said nitrile polymer and about 20.0 to 10.0weight percent of said modifying interpolymer, said nitrile polymercontaining at least about 75.0 weight percent of said ethylenicallyunsaturated monomer and said modifying interpolymer comprising about25.0 to 40.0 weight percent of dicyanobutene-1 and about 75.0 to 60.0weight percent of said copolymerizable monomer.
 5. The blend of claim 2wherein said preformed rubbery polymer is a diene rubber and at least aportion of said nitrile polymer is grafted thereupon.
 6. The blend ofclaim 2 wherein said preformed rubbery polymer is a diene rubber presentin an amount of about 5.0 to 15.0 percent based upon the weight of saidmodifying interpolymer, and wherein at least a portion of said modifyinginterpolymer is grafted thereupon.
 7. The blend of claim 1 wherein saidnitrile polymer is selected from the group consisting of acrylonitrilehomopolymers and copolymers thereof with a monomer selected from theclass consisting of styrene, alpha-alkyl styrenes, ring chlorinatedanalogs of styrene and alpha-alkyl styrenes, (alk)acrylic acids,(alk)acrylic acid esters, vinyl esters and mixtures thereof, saiddicyanobutene-1 being 2,4-dicyanobutene-1.
 8. The blend of claim 1wherein said nitrile polymer is selected from the group consisting ofmethacrylonitrile homopolymers and copolymers thereof with a monomerselected from the class consisting of styrene, alpha-alkyl styrenes,ring chlorinated analogs of styrene and alpha-alkyl styrenes,(alk)acrylic acids, (alk)acrylic acid esters and mixtures thereof, saiddicyanobutene-1 being 2,4dicyanobutene-1.
 9. The blend of claim 1wherein said nitrile polymer has a weight average molecular weight of atleast about 250,000.